Q: how to get rid of the spinning beachball

Spinning indicator usually raised from insufficien resources, be they CPU cycles, free storage, or lock of free RAM memory.

Restarting the Mac is often sufficient to bring it back to usual performance, but do check your free storage amount.

Otherwise, you can try Safe Boot mode by holding down the Shift key at startup. Safe Boot is quite slow because the OS performs a bunch of cleanup and verification tasks, so give it time. After you're completely logged in, restart normally.

Safari/Preferences/Advanced - enable the Develop menu, then go there and Empty Caches. Quit/reopen Safari and test. Then try Safari/History/Show History and delete all history items.  Quit/reopen Safari and test. You can also try try Safari/Clear History…. The down side is it clears all cookies. Doing this may cause some sites to no longer recognize your computer as one that has visited the web site. Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J.  When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder.  Select Library./Caches/com.apple.Safari/Cache.db and move it to the trash.

Go to Safari Preferences/Extensions and turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

Safari Corruption       See post by Linc Davis